// Source: https://github.com/System-Glitch/SHA256

#pragma once

#include <string>
#include <array>
#include <cstdint>

class SHA256 {

public:
    SHA256();
    void update(const uint8_t * data, size_t length);
    void update(const std::string &data);
    std::array<uint8_t, 32> digest();

    static std::string toString(const std::array<uint8_t, 32> & digest);

private:
    uint8_t  m_data[64];
    uint32_t m_blocklen;
    uint64_t m_bitlen;
    uint32_t m_state[8]; //A, B, C, D, E, F, G, H

    static constexpr std::array<uint32_t, 64> K = {
        0x428a2f98,0x71374491,0xb5c0fbcf,0xe9b5dba5,
        0x3956c25b,0x59f111f1,0x923f82a4,0xab1c5ed5,
        0xd807aa98,0x12835b01,0x243185be,0x550c7dc3,
        0x72be5d74,0x80deb1fe,0x9bdc06a7,0xc19bf174,
        0xe49b69c1,0xefbe4786,0x0fc19dc6,0x240ca1cc,
        0x2de92c6f,0x4a7484aa,0x5cb0a9dc,0x76f988da,
        0x983e5152,0xa831c66d,0xb00327c8,0xbf597fc7,
        0xc6e00bf3,0xd5a79147,0x06ca6351,0x14292967,
        0x27b70a85,0x2e1b2138,0x4d2c6dfc,0x53380d13,
        0x650a7354,0x766a0abb,0x81c2c92e,0x92722c85,
        0xa2bfe8a1,0xa81a664b,0xc24b8b70,0xc76c51a3,
        0xd192e819,0xd6990624,0xf40e3585,0x106aa070,
        0x19a4c116,0x1e376c08,0x2748774c,0x34b0bcb5,
        0x391c0cb3,0x4ed8aa4a,0x5b9cca4f,0x682e6ff3,
        0x748f82ee,0x78a5636f,0x84c87814,0x8cc70208,
        0x90befffa,0xa4506ceb,0xbef9a3f7,0xc67178f2
    };

    static uint32_t rotr(uint32_t x, uint32_t n);
    static uint32_t choose(uint32_t e, uint32_t f, uint32_t g);
    static uint32_t majority(uint32_t a, uint32_t b, uint32_t c);
    static uint32_t sig0(uint32_t x);
    static uint32_t sig1(uint32_t x);
    void transform();
    void pad();
    void revert(std::array<uint8_t, 32> & hash);
};
